Examining the characteristics and implications of sensor side channels

The nodes in wireless sensor networks (WSNs) utilize the radio frequency (RF) channel to communicate. Given that the RF channel is the primary communication channel, many researchers have developed techniques for securing that channel. However, the RF channel is not the only interface into a sensor. The sensing components, which are primarily designed to sense characteristics about the outside world, can also be used (or misused) as a communication (side) channel. In this paper, we characterize the side channels for various sensory components (i.e., light sensor, acoustic sensor, and accelerometer). While previous work has focused on the use of these side channels to improve the security and performance of a WSN, we seek to determine if the side channels have enough capacity to potentially be used for malicious activity. Specifically, we evaluate the feasibility and practicality of the side channels using today´s sensor technology and illustrate that these channels have enough capacity to enable the transfer of common, well-known malware. The ultimate goal of this work is to illustrate the need for intrusion detection systems (IDSs) that not only monitor the RF channel, but also monitor the values returned by the sensory components.